The present invention relates to a new and improved force transmitting apparatus and method which are used to control a variable load.
The force transmitting apparatus is particularly useful as a brake in a drilling system having a draw string which is subjected to large tension forces by pipe connected with a drill bit. The force transmitting apparatus retards rotation of a winch drum connected with the draw string to control the tension in the draw string. Controlling tension in the draw string enables the force applied against the drill bit by the pipe to be controlled.
It has been suggested that a brake for a winch drum in a drilling system include seven force transmitting discs to provide a large braking force to offset large tension forces in the draw string. Control fluid pressure is supplied to the brake to control operation of the brake. The control fluid pressure supplied to the brake is varied to vary the tension in the draw string. The large number of force transmitting discs in the brake causes the tension in the draw string to change significantly with a very small change in control fluid pressure.